diff --git a/src/app/CMakeLists.txt b/src/app/CMakeLists.txt
index cb8dacab0..5ba751635 100644
--- a/src/app/CMakeLists.txt
+++ b/src/app/CMakeLists.txt
@@ -258,6 +258,7 @@ add_library(app-lib
   document_range.cpp
   document_range_ops.cpp
   document_undo.cpp
+  extra_cel.cpp
   file/ase_format.cpp
   file/bmp_format.cpp
   file/file.cpp
diff --git a/src/app/cmd/set_pixel_format.cpp b/src/app/cmd/set_pixel_format.cpp
index 1459e39f4..e7303ed97 100644
--- a/src/app/cmd/set_pixel_format.cpp
+++ b/src/app/cmd/set_pixel_format.cpp
@@ -105,7 +105,7 @@ void SetPixelFormat::setFormat(PixelFormat format)
 
   // Regenerate extras
   static_cast<app::Document*>(sprite->document())
-    ->destroyExtraCel();
+    ->setExtraCel(ExtraCelRef(nullptr));
 
   // Generate notification
   DocumentEvent ev(sprite->document());
diff --git a/src/app/commands/cmd_fullscreen_preview.cpp b/src/app/commands/cmd_fullscreen_preview.cpp
index f3f1482f7..79c30263d 100644
--- a/src/app/commands/cmd_fullscreen_preview.cpp
+++ b/src/app/commands/cmd_fullscreen_preview.cpp
@@ -66,7 +66,7 @@ public:
     editor->getManager()->freeMouse();
 
     // Clear extras (e.g. pen preview)
-    m_doc->destroyExtraCel();
+    m_doc->setExtraCel(ExtraCelRef(nullptr));
 
     gfx::Rect vp = view->getViewportBounds();
     gfx::Point scroll = view->getViewScroll();
diff --git a/src/app/commands/cmd_undo.cpp b/src/app/commands/cmd_undo.cpp
index 0b38c3106..e0d0ce1ef 100644
--- a/src/app/commands/cmd_undo.cpp
+++ b/src/app/commands/cmd_undo.cpp
@@ -122,7 +122,7 @@ void UndoCommand::onExecute(Context* context)
   }
 
   document->generateMaskBoundaries();
-  document->destroyExtraCel(); // Regenerate extras
+  document->setExtraCel(ExtraCelRef(nullptr));
 
   update_screen_for_document(document);
   set_current_palette(writer.palette(), false);
diff --git a/src/app/document.cpp b/src/app/document.cpp
index ed0092f67..839e415ef 100644
--- a/src/app/document.cpp
+++ b/src/app/document.cpp
@@ -51,12 +51,6 @@ Document::Document(Sprite* sprite)
   , m_read_locks(0)
     // Information about the file format used to load/save this document
   , m_format_options(NULL)
-    // Extra cel
-  , m_extraCel(nullptr)
-  , m_extraImage(nullptr)
-  , m_extraImageBuffer(nullptr)
-  , m_extraCelBlendMode(BlendMode::NORMAL)
-  , m_extraCelType(render::ExtraType::NONE)
   // Mask
   , m_mask(new Mask())
   , m_maskVisible(true)
@@ -75,8 +69,6 @@ Document::~Document()
   // which could result in serious problems for observers expecting a
   // fully created app::Document.
   ASSERT(context() == NULL);
-
-  destroyExtraCel();
 }
 
 DocumentApi Document::getApi(Transaction& transaction)
@@ -232,55 +224,6 @@ void Document::generateMaskBoundaries(const Mask* mask)
   notifySelectionChanged();
 }
 
-//////////////////////////////////////////////////////////////////////
-// Extra Cel (it is used to draw pen preview, pixels in movement, etc.)
-
-void Document::destroyExtraCel()
-{
-  delete m_extraCel;
-
-  m_extraCel = nullptr;
-  m_extraImage.reset(nullptr);
-  m_extraCelType = render::ExtraType::NONE;
-}
-
-void Document::prepareExtraCel(const gfx::Rect& bounds, frame_t frame, int opacity)
-{
-  ASSERT(sprite() != NULL);
-
-  if (!m_extraImage ||
-      m_extraImage->pixelFormat() != sprite()->pixelFormat() ||
-      m_extraImage->width() != bounds.w ||
-      m_extraImage->height() != bounds.h) {
-    if (!m_extraImageBuffer)
-      m_extraImageBuffer.reset(new ImageBuffer(1));
-    Image* newImage = Image::create(sprite()->pixelFormat(), bounds.w, bounds.h, m_extraImageBuffer);
-    m_extraImage.reset(newImage);
-  }
-
-  if (!m_extraCel)
-    m_extraCel = new Cel(frame_t(0), ImageRef(NULL)); // Ignored fields for this cel (frame, and image index)
-
-  m_extraCel->setPosition(bounds.getOrigin());
-  m_extraCel->setOpacity(opacity);
-  m_extraCel->setFrame(frame);
-}
-
-void Document::setExtraCelType(render::ExtraType type)
-{
-  m_extraCelType = type;
-}
-
-Cel* Document::getExtraCel() const
-{
-  return m_extraCel;
-}
-
-Image* Document::getExtraCelImage() const
-{
-  return m_extraImage.get();
-}
-
 //////////////////////////////////////////////////////////////////////
 // Mask
 
diff --git a/src/app/document.h b/src/app/document.h
index 03b7bb1d8..bf776f3a5 100644
--- a/src/app/document.h
+++ b/src/app/document.h
@@ -9,6 +9,7 @@
 #define APP_DOCUMENT_H_INCLUDED
 #pragma once
 
+#include "app/extra_cel.h"
 #include "app/file/format_options.h"
 #include "base/disable_copying.h"
 #include "base/mutex.h"
@@ -19,12 +20,9 @@
 #include "doc/color.h"
 #include "doc/document.h"
 #include "doc/frame.h"
-#include "doc/image_ref.h"
-#include "doc/image_buffer.h"
 #include "doc/pixel_format.h"
 #include "gfx/rect.h"
 #include "gfx/transformation.h"
-#include "render/extra_type.h"
 
 #include <string>
 
@@ -123,14 +121,8 @@ namespace app {
     //////////////////////////////////////////////////////////////////////
     // Extra Cel (it is used to draw pen preview, pixels in movement, etc.)
 
-    void prepareExtraCel(const gfx::Rect& bounds, frame_t frame, int opacity);
-    void setExtraCelType(render::ExtraType type);
-    void destroyExtraCel();
-    Cel* getExtraCel() const;
-    Image* getExtraCelImage() const;
-    render::ExtraType getExtraCelType() const { return m_extraCelType; }
-    BlendMode getExtraCelBlendMode() const { return m_extraCelBlendMode; }
-    void setExtraCelBlendMode(BlendMode mode) { m_extraCelBlendMode = mode; }
+    ExtraCelRef extraCel() const { return m_extraCel; }
+    void setExtraCel(const ExtraCelRef& extraCel) { m_extraCel = extraCel; }
 
     //////////////////////////////////////////////////////////////////////
     // Mask
@@ -210,13 +202,7 @@ namespace app {
     base::SharedPtr<FormatOptions> m_format_options;
 
     // Extra cel used to draw extra stuff (e.g. editor's pen preview, pixels in movement, etc.)
-    Cel* m_extraCel;
-
-    // Image of the extra cel.
-    ImageRef m_extraImage;
-    ImageBufferPtr m_extraImageBuffer;
-    BlendMode m_extraCelBlendMode;
-    render::ExtraType m_extraCelType;
+    ExtraCelRef m_extraCel;
 
     // Current mask.
     base::UniquePtr<Mask> m_mask;
diff --git a/src/app/extra_cel.cpp b/src/app/extra_cel.cpp
new file mode 100644
index 000000000..529689238
--- /dev/null
+++ b/src/app/extra_cel.cpp
@@ -0,0 +1,53 @@
+// Aseprite
+// Copyright (C) 2001-2015  David Capello
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "app/extra_cel.h"
+
+#include "doc/sprite.h"
+
+namespace app {
+
+ExtraCel::ExtraCel()
+  : m_type(render::ExtraType::NONE)
+  , m_blendMode(doc::BlendMode::NORMAL)
+{
+}
+
+void ExtraCel::create(doc::Sprite* sprite,
+                      const gfx::Rect& bounds,
+                      doc::frame_t frame,
+                      int opacity)
+{
+  ASSERT(sprite);
+
+  if (!m_image ||
+      m_image->pixelFormat() != sprite->pixelFormat() ||
+      m_image->width() != bounds.w ||
+      m_image->height() != bounds.h) {
+    if (!m_imageBuffer)
+      m_imageBuffer.reset(new doc::ImageBuffer(1));
+    doc::Image* newImage = doc::Image::create(sprite->pixelFormat(),
+                                              bounds.w, bounds.h,
+                                              m_imageBuffer);
+    m_image.reset(newImage);
+  }
+
+  if (!m_cel) {
+    // Ignored fields for this cel (frame, and image index)
+    m_cel.reset(new doc::Cel(doc::frame_t(0), doc::ImageRef(nullptr)));
+  }
+
+  m_cel->setPosition(bounds.getOrigin());
+  m_cel->setOpacity(opacity);
+  m_cel->setFrame(frame);
+}
+
+} // namespace app
diff --git a/src/app/extra_cel.h b/src/app/extra_cel.h
new file mode 100644
index 000000000..9c4f76255
--- /dev/null
+++ b/src/app/extra_cel.h
@@ -0,0 +1,58 @@
+// Aseprite
+// Copyright (C) 2001-2015  David Capello
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License version 2 as
+// published by the Free Software Foundation.
+
+#ifndef APP_EXTRA_CEL_H_INCLUDED
+#define APP_EXTRA_CEL_H_INCLUDED
+#pragma once
+
+#include "base/disable_copying.h"
+#include "base/unique_ptr.h"
+#include "doc/blend_mode.h"
+#include "doc/cel.h"
+#include "doc/frame.h"
+#include "doc/image_buffer.h"
+#include "doc/image_ref.h"
+#include "gfx/rect.h"
+#include "render/extra_type.h"
+
+namespace doc {
+  class Sprite;
+}
+
+namespace app {
+
+  class ExtraCel {
+  public:
+    ExtraCel();
+
+    void create(doc::Sprite* sprite, const gfx::Rect& bounds, doc::frame_t frame, int opacity);
+    void destroy();
+
+    render::ExtraType type() const { return m_type; }
+    void setType(render::ExtraType type) { m_type = type; }
+
+    doc::Cel* cel() const { return m_cel.get(); }
+    doc::Image* image() const { return m_image.get(); }
+
+    doc::BlendMode blendMode() const { return m_blendMode; }
+    void setBlendMode(doc::BlendMode mode) { m_blendMode = mode; }
+
+  private:
+    render::ExtraType m_type;
+    base::UniquePtr<doc::Cel> m_cel;
+    doc::ImageRef m_image;
+    doc::ImageBufferPtr m_imageBuffer;
+    doc::BlendMode m_blendMode;
+
+    DISABLE_COPYING(ExtraCel);
+  };
+
+  typedef base::SharedPtr<ExtraCel> ExtraCelRef;
+
+} // namespace app
+
+#endif
diff --git a/src/app/ui/editor/brush_preview.cpp b/src/app/ui/editor/brush_preview.cpp
index 6f0da6362..8d190b074 100644
--- a/src/app/ui/editor/brush_preview.cpp
+++ b/src/app/ui/editor/brush_preview.cpp
@@ -155,13 +155,17 @@ void BrushPreview::show(const gfx::Point& screenPos)
     if (cel) opacity = MUL_UN8(opacity, cel->opacity(), t);
     if (layer) opacity = MUL_UN8(opacity, static_cast<LayerImage*>(layer)->opacity(), t);
 
-    document->prepareExtraCel(brushBounds, site.frame(), opacity);
-    document->setExtraCelType(render::ExtraType::NONE);
-    document->setExtraCelBlendMode(
+    if (!m_extraCel)
+      m_extraCel.reset(new ExtraCel);
+    m_extraCel->create(document->sprite(), brushBounds, site.frame(), opacity);
+    m_extraCel->setType(render::ExtraType::NONE);
+    m_extraCel->setBlendMode(
       (layer ? static_cast<LayerImage*>(layer)->blendMode():
                BlendMode::NORMAL));
 
-    Image* extraImage = document->getExtraCelImage();
+    document->setExtraCel(m_extraCel);
+
+    Image* extraImage = m_extraCel->image();
     extraImage->setMaskColor(mask_index);
     clear_image(extraImage,
                 (extraImage->pixelFormat() == IMAGE_INDEXED ? mask_index: 0));
@@ -173,7 +177,7 @@ void BrushPreview::show(const gfx::Point& screenPos)
         BlendMode::SRC);
 
       // This extra cel is a patch for the current layer/frame
-      document->setExtraCelType(render::ExtraType::PATCH);
+      m_extraCel->setType(render::ExtraType::PATCH);
     }
 
     tools::ToolLoop* loop = create_tool_loop_preview(
@@ -247,7 +251,7 @@ void BrushPreview::hide()
 
   // Clean pixel/brush preview
   if (m_withRealPreview) {
-    document->destroyExtraCel();
+    document->setExtraCel(ExtraCelRef(nullptr));
     document->notifySpritePixelsModified(
       sprite, gfx::Region(m_lastBounds), m_lastFrame);
 
diff --git a/src/app/ui/editor/brush_preview.h b/src/app/ui/editor/brush_preview.h
index 3fbaac738..701be8160 100644
--- a/src/app/ui/editor/brush_preview.h
+++ b/src/app/ui/editor/brush_preview.h
@@ -9,6 +9,7 @@
 #define APP_UI_EDITOR_BRUSH_PREVIEW_H_INCLUDED
 #pragma once
 
+#include "app/extra_cel.h"
 #include "base/shared_ptr.h"
 #include "doc/color.h"
 #include "doc/frame.h"
@@ -106,6 +107,8 @@ namespace app {
     // brush preview in the exact same place.
     gfx::Rect m_lastBounds;
     doc::frame_t m_lastFrame;
+
+    ExtraCelRef m_extraCel;
   };
 
   class HideBrushPreview {
diff --git a/src/app/ui/editor/editor.cpp b/src/app/ui/editor/editor.cpp
index 0969298b0..a6cab19e5 100644
--- a/src/app/ui/editor/editor.cpp
+++ b/src/app/ui/editor/editor.cpp
@@ -479,14 +479,13 @@ void Editor::drawOneSpriteUnclippedRect(ui::Graphics* g, const gfx::Rect& sprite
       }
     }
 
-    if (m_document->getExtraCelType() != render::ExtraType::NONE) {
-      ASSERT(m_document->getExtraCel());
-
+    ExtraCelRef extraCel = m_document->extraCel();
+    if (extraCel && extraCel->type() != render::ExtraType::NONE) {
       m_renderEngine.setExtraImage(
-        m_document->getExtraCelType(),
-        m_document->getExtraCel(),
-        m_document->getExtraCelImage(),
-        m_document->getExtraCelBlendMode(),
+        extraCel->type(),
+        extraCel->cel(),
+        extraCel->image(),
+        extraCel->blendMode(),
         m_layer, m_frame);
     }
 
@@ -794,22 +793,24 @@ void Editor::flashCurrentLayer()
   if (src_image) {
     m_renderEngine.removePreviewImage();
 
-    m_document->prepareExtraCel(m_sprite->bounds(), m_frame, 255);
-    m_document->setExtraCelType(render::ExtraType::COMPOSITE);
-
-    Image* flash_image = m_document->getExtraCelImage();
+    ExtraCelRef extraCel(new ExtraCel);
+    extraCel->create(m_sprite, m_sprite->bounds(), m_frame, 255);
+    extraCel->setType(render::ExtraType::COMPOSITE);
+    extraCel->setBlendMode(BlendMode::NEG_BW);
 
+    Image* flash_image = extraCel->image();
     clear_image(flash_image, flash_image->maskColor());
     copy_image(flash_image, src_image, x, y);
-    m_document->setExtraCelBlendMode(BlendMode::NEG_BW);
 
-    drawSpriteClipped(gfx::Region(
-        gfx::Rect(0, 0, m_sprite->width(), m_sprite->height())));
+    {
+      ExtraCelRef oldExtraCel = m_document->extraCel();
+      m_document->setExtraCel(extraCel);
+      drawSpriteClipped(gfx::Region(
+                          gfx::Rect(0, 0, m_sprite->width(), m_sprite->height())));
+      getManager()->flipDisplay();
+      m_document->setExtraCel(oldExtraCel);
+    }
 
-    getManager()->flipDisplay();
-
-    m_document->setExtraCelBlendMode(BlendMode::NORMAL);
-    m_document->destroyExtraCel();
     invalidate();
   }
 }
diff --git a/src/app/ui/editor/pixels_movement.cpp b/src/app/ui/editor/pixels_movement.cpp
index 300fa335f..9cc2ba6b4 100644
--- a/src/app/ui/editor/pixels_movement.cpp
+++ b/src/app/ui/editor/pixels_movement.cpp
@@ -89,7 +89,7 @@ PixelsMovement::PixelsMovement(
   // The extra cel must be null, because if it's not null, it means
   // that someone else is using it (e.g. the editor brush preview),
   // and its owner could destroy our new "extra cel".
-  ASSERT(!m_document->getExtraCel());
+  ASSERT(!m_document->extraCel());
   redrawExtraImage();
   redrawCurrentMask();
 
@@ -491,8 +491,8 @@ void PixelsMovement::getDraggedImageCopy(base::UniquePtr<Image>& outputImage,
 
 void PixelsMovement::stampImage()
 {
-  const Cel* cel = m_document->getExtraCel();
-  const Image* image = m_document->getExtraCelImage();
+  const Cel* cel = m_extraCel->cel();
+  const Image* image = m_extraCel->image();
 
   ASSERT(cel && image);
 
@@ -583,7 +583,7 @@ void PixelsMovement::dropImage()
   // Destroy the extra cel (this cel will be used by the drawing
   // cursor surely).
   ContextWriter writer(m_reader, 1000);
-  m_document->destroyExtraCel();
+  m_document->setExtraCel(ExtraCelRef(nullptr));
 }
 
 void PixelsMovement::discardImage(bool commit)
@@ -599,7 +599,7 @@ void PixelsMovement::discardImage(bool commit)
   // Destroy the extra cel and regenerate the mask boundaries (we've
   // just deselect the mask).
   ContextWriter writer(m_reader, 1000);
-  m_document->destroyExtraCel();
+  m_document->setExtraCel(ExtraCelRef(nullptr));
   m_document->generateMaskBoundaries();
 }
 
@@ -610,8 +610,8 @@ bool PixelsMovement::isDragging() const
 
 gfx::Rect PixelsMovement::getImageBounds()
 {
-  const Cel* cel = m_document->getExtraCel();
-  const Image* image = m_document->getExtraCelImage();
+  const Cel* cel = m_extraCel->cel();
+  const Image* image = m_extraCel->image();
 
   ASSERT(cel != NULL);
   ASSERT(image != NULL);
@@ -641,14 +641,16 @@ void PixelsMovement::redrawExtraImage()
   if (cel) opacity = MUL_UN8(opacity, cel->opacity(), t);
 
   gfx::Rect bounds = m_currentData.transformedBounds();
-  m_document->prepareExtraCel(bounds, m_site.frame(), opacity);
-  m_document->setExtraCelType(render::ExtraType::PATCH);
-  m_document->setExtraCelBlendMode(
-    static_cast<LayerImage*>(m_layer)->blendMode());
+
+  m_extraCel.reset(new ExtraCel);
+  m_extraCel->create(m_document->sprite(), bounds, m_site.frame(), opacity);
+  m_extraCel->setType(render::ExtraType::PATCH);
+  m_extraCel->setBlendMode(static_cast<LayerImage*>(m_layer)->blendMode());
+  m_document->setExtraCel(m_extraCel);
 
   // Draw the transformed pixels in the extra-cel which is the chunk
   // of pixels that the user is moving.
-  drawImage(m_document->getExtraCelImage(), bounds.getOrigin(), true);
+  drawImage(m_extraCel->image(), bounds.getOrigin(), true);
 }
 
 void PixelsMovement::redrawCurrentMask()
diff --git a/src/app/ui/editor/pixels_movement.h b/src/app/ui/editor/pixels_movement.h
index cc02e5821..abf6df7c0 100644
--- a/src/app/ui/editor/pixels_movement.h
+++ b/src/app/ui/editor/pixels_movement.h
@@ -10,6 +10,7 @@
 #pragma once
 
 #include "app/context_access.h"
+#include "app/extra_cel.h"
 #include "app/transaction.h"
 #include "app/ui/editor/handle_type.h"
 #include "base/connection.h"
@@ -125,6 +126,7 @@ namespace app {
     ScopedConnection m_pivotVisConn;
     ScopedConnection m_pivotPosConn;
     ScopedConnection m_rotAlgoConn;
+    ExtraCelRef m_extraCel;
   };
 
   inline PixelsMovement::MoveModifier& operator|=(PixelsMovement::MoveModifier& a,